Document Type

Article

Publication Date

January 2012

Abstract

To understand the effects of Wolbachia in Andricus mairei Kieffer , an oak gall wasp ( Cynipini, Cynipidae) that forms clusters of up to 30 monothalamous galls in the catkins of Quercus glandulifera var. brevipetiolata Nakai, we examined the presence and infection frequency of Wolbachia in three widely separated geographic populations of A. mairei in Hunan Province, South China, using polymerase chain reaction and sequence determination of the wsp gene of Wolbachia from the three populations. Our survey results showed that Wolbachia infection rates were unusually high in the three test populations : 100% for the male wasps from all populations , while 100% , 100% and 80% for the Yueyang, Changsha and Shaoyang populations of the female wasps, respectively. The sequencing results showed that the gene from all the three populations is 561 bp in length. Comparison with the wsp gene sequences in A. mairei and Neuroterus macropterus , Biorhiza pallida , Andricus solitarius ( strain 1 ) and Synergus crassicornis revealed a 95% identity. The phylogenie relationship of Wolbachia strains in Cynipidae with the known wsp sequences indicated that the Wolbachia strain of A. mairei is closely related to that of N. macropterus , B. pallida, A. solitarius ( strain 1 ) , and S. crassicornis , and belongs to the A group. We also discovered strikingly male-biased sex ratios in all the test populations: females only accounted for 15.3%, 12. 1%, and 19. 8% of the Yueyang, Changsha, and Shaoyang populations, respectively, indicating the extremely male-biased sex ratios. These results suggest that the symbiosis of Wolbachia with A. mairei does not induce parthenogenesis in A. mairei, which can not be properly explained and is worth further investigation.